It has been known for some time that gastrin, histamine, and acetylcholine regulate the secretion of acid in the gastric mucosa, but the precise nature of the interaction of these stimuli as well as their action on the parietal cell is still unknown. The purpose of the present investigation is to delineate the biochemical events which occur in the parietal cell in response to these hormones. In particular, attempts will be made to evaluate the roles, if any, of cyclic nucleotides, calcium, and cyclic nucleotide-dependent and -independent protein kinases in the mechanism of action of the secretagogues. It is hoped that through a study of the effects of these hormones on isolated cells, the proposed research will provide further insight into the biochemical basis of the gastric secretory process as well as those factors associated with gastric diseases.